FIG. 6 illustrates a conventionally known steering device for an automobile. A steering wheel 1 is supported by and fastened to the rear-end section of a steering shaft 5, and this steering shaft 5 is passed in the axial direction through a cylindrical shaped steering column 6 and supported by the steering column 6 to as to rotate freely. The front-end section of the steering shaft 5 is connected to the rear-end section of an intermediate shaft 8 by way of a universal joint 7, and the front-end section of this intermediate shaft 8 is connected to an input shaft 3 by way of a different universal joint 9. When the operator operates the steering wheel 1, the rotation of this steering wheel 1 is transmitted to the input shaft 3 of a steering-gear unit 2 by way of the universal joint 7, the intermediate shaft 8 and the universal joint 9, and as this input shaft 3 rotates, a pair of left and right tie rods 4,4 are pushed and pulled, applying a steering angle to the front wheels.
An electric-powered power steering device is assembled in the steering device for an automobile illustrated in FIG. 6. An electric motor 10, which is the power source for applying an auxiliary force, is supported by a housing 11 that is fastened to the front-end section of the steering column 6. The output torque (auxiliary force) from the electric motor 10 is applied to the steering shaft 5 by way of a reducer or the like that is provided inside the housing 11.
A steering column device for an automobile in which a tilt mechanism for adjusting the up-down position of the steering wheel 1 and/or a telescopic mechanism for adjusting the forward-backward position of the steering wheel 1 according to the physique and driving posture of the operator are assembled is known and disclosed in JP2009227181 (A). In order to construct a tilt mechanism, the front-end section of a housing 11 is supported by the vehicle body 12 by way of a tilt shaft 13 that is arranged in the width direction (the width direction signifies the width direction of the vehicle body, and corresponds to the left-right direction) so as to be able to pivotally displace. A displacement bracket 14 is provided on the bottom surface of the middle section in the axial direction of the steering column 6, and a support bracket 15 is provided so as to sandwich the displacement bracket 14 from both sides in the width direction. The support bracket 15 includes an installation section 16 that is provided on the top section, and a pair of left and right support-plate sections 17 that hang downward from the installation-plate section 16, and the support bracket 15 is supported by the vehicle body by way of this installation-plate section 16.
Long tilt holes 18 that are circular arc shaped centered around the tilt shaft 13 and that extend in the up-down direction are formed in the pair of support-plate sections 17, and through holes 19 are formed in portions of the displacement bracket 14 that are aligned with part of the long tilt holes 18. The construction illustrated in FIG. 6 is construction in which a tilt and telescopic mechanism is assembled, making it possible to adjust the forward-backward position of the steering wheel 1 in addition to the up-down position, so the through holes 19 are long holes that extend in the axial direction of the steering shaft 5 and steering column 6, making it possible to expand or contract the steering shaft 5 and steering column 6.
FIG. 7 to FIG. 8 illustrate in more detail the construction of a tilt-type steering device in which a telescopic mechanism is assembled. The steering column 6 is constructed such that the front section of the outer column 20 that is located on the rear side and the rear section of the inner column 21 that is located on the front side fit together so that sliding movement is possible, and so that the overall length can be expanded or contracted. The outer column 20 is manufactured by die cast molding of a light alloy metal, for example, and by providing a slit 22 in the front section of the outer column 20, the inner diameter of the front section of this outer column 20 is able to elastically expand or contract. A pair of held plate sections 23 are provided in portions that are located on both sides in the width direction of the slit 22, and the displacement bracket 14 is formed by that pair of held plate sections 23. Through holes 19 that extend in the axial direction of the steering column 6 are formed in the pair of held plate sections 23. The pair of support-plate sections 17 of the support bracket 15 are located in portions that hold the displacement bracket 14 on both sides in the width direction, and long tilt holes 18 that have a partial arc shape centered around a tilt shaft 13 (see FIG. 6) and that extend in the up-down direction are formed in the pair of support-plate sections 17. A rod-shaped member 24 that is arranged in the width direction is inserted through the long tilt holes 18 and the through holes 19.
An adjustment lever 25 is provided on one end section in the axial direction of the rod-shaped member 24, an anchor section 26 is provided on the other end section in the axial direction of the rod-shaped member 24, and a cam device 27 is provided in a portion near the one end section of the middle section in the axial direction of the rod-shaped member 24. A tilt lock mechanism is constructed so that the space between the inside surfaces of the pair of support-plate sections 17 can be expanded or contracted by a tilting movement of the adjustment lever 25. The anchor section 26 has a shape like the head section of a bolt, and is such that a first engaging convex section 28 that is formed on the inside surface of the anchor section 26 engages with a long tilt holes 18 that is formed in the support-plate section 17 on the other end section side (support-plate section 17 on the right in FIG. 8) that faces the inside surface of the anchor section so that only displacement along this long tilt hole 18 is possible. The rod-shaped member 24 can be raised or lowered along the long tilt holes 18, however rotation of the rod-shaped member 24 around the center axis thereof is essentially suppressed.
A cam device 27 such as illustrated in FIG. 9 is assembled in the tilt-type steering device. The cam device 27 includes a drive-side cam 29 and a driven-side cam 30. The drive-side cam 29 is formed into an annular plate shape (the outer-circumferential surface is a cylindrical shape) having a center hole 30 through which the rod-shaped member 24 is inserted, and a drive-side cam surface 33 is formed on the inside surface in the width direction. The drive-side cam surface 33 includes a flat shaped drive-side basal surface 35, and drive-side convex sections 36 that are provided so as to protrude inward in the width direction from plural evenly spaced locations in the circumferential direction of the drive-side basal surface 35. The driven-side cam 30 is formed into an annular plate shape (the outer-circumferential surface is a cylindrical shape) having a center hole 32 through which the rod-shaped member 24 is inserted, a driven-side cam surface 34 is formed on the outside surface in the width direction that faces the drive-side cam surface 33 when cam device 27 is constructed, and a second engaging convex section 39 is formed on the inside surface in the width direction. The driven-side cam surface 34 includes a flat shaped driven-side basal surface 37, and driven-side convex sections 38 that are provided so as to protrude outward in the width direction from plural evenly spaced locations in the circumferential direction of the driven-side basal surface 37. In the example in FIG. 9, the outer diameter of the drive-side cam 29 and the outer diameter of the driven-side cam are the same as each other.
The driven-side cam 30 causes the second engaging convex section 39 to engage in the long tilt hole 18 that is formed in the support-plate section 17 on the one end section side (support-plate section 17 on the left in FIG. 8) of the pair of support-plate sections 17 that faces the inside surface in the width direction of the driven-side cam 30 so that only displacement along that long tilt hole 18 is possible. The driven-side cam 30 can raise or lower along this long tilt hole 18, however, does not rotate around its own axis. By connecting and fastening the base-end section of the adjustment lever 25 to the drive-side cam 29, the drive-side cam 29 rotates back-and-forth around the rod-shaped member 24 as the adjustment lever 25 is tilted back-and-forth. A thrust bearing 41 is provided between a nut 40 that is screwed onto one end section in the axial direction of the rod-shaped member 24 and the outside surface of the base-end section of the adjustment lever 25, which makes it possible for the drive-side cam 29 to rotate back-and-forth while at the same time supporting a thrust load that is applied to the drive-side cam 29. The nut 40 can be prevented from becoming loose by crimping or the like.
By tilting the adjustment lever 25 in a specified direction (generally downward) when adjusting the position of the steering wheel 1, the drive-side cam 29 is rotated in a direction that unlocks the cam device 27. As a result, as illustrated in FIG. 10C, by alternatingly arranging the drive-side convex sections 36 and the driven-side convex sections 38 in the circumferential direction, the dimension in the axial direction of the cam device 27 is in the contracted unlocked state, and the space between the driven-side cam 30, which corresponds to a pressure section, and the anchor section 26 expands. As a result, the surface pressure at the areas of contact between the inside surfaces of the pair of support-plate sections 17 and the outside surfaces of the pair of held-plate sections 23 decreases until it is lost, and at the same time, the inner diameter of the front-end section of the outer column 20 elastically expands, and the surface pressure at the area of contact between the inner-circumferential surface of the front-end section of the outer column 20 and the outer-circumferential surface of the rear-end section of the inner column 21 decreases. In this state, it becomes possible to adjust the up-down position and the forward-backward position of the steering wheel within the range that the rod-shaped member 24 is able to move inside the long tilt holes 18 and the through holes 19.
In order to maintain the steering wheel 1 at the desired position, the adjustment lever 25 is tilted in the opposite direction (generally upward) after the steering wheel 1 has been moved to the desired position. As a result, as illustrated in FIG. 10A, the tip-end surfaces of the drive-side convex sections 36 and the tip-end surfaces of the driven-side convex sections 38 are brought in contact with each other, the dimension in the axial direction of the cam device 27 is set to the expanded locked state, and the space between the inside surfaces of the pair of support-plate sections 17 contracts. In this state, the surface pressure at the areas of contact between the inside surfaces of the pair of support-plate sections 17 and the outside surfaces of the pair of held-plate sections 23 increases, and at the same time, the inner diameter of the front-end section of the outer column 20 elastically contracts, the surface pressure at the area of contact between the inner-circumferential surface of the front-end section of the output column 20 and the outer-circumferential surface of the rear-end section of the inner column 21 increases, and the steering wheel 1 is maintained at the adjusted position.
The tilting angle of the adjustment lever 25 when the steering wheel 1 is maintained in the desired position is determined by design according to the installation specifications for installing the tilt-type steering device into the vehicle body such as the inclination angle of the center axis of the steering column 6 with respect to the forward-backward direction, the shape of the column cover, and the relationship with other parts such as a combination switch that is located in a portion near the steering wheel 1, and is set so that there is no interference with the operation of the steering wheel 1 and the operation of the accelerator pedal and brake pedal. Adjustment of the tilting angle of the adjustment lever 25 is performed by selecting an appropriate width in the circumferential direction of the drive-side convex sections 36 and the driven-side convex sections 38 as the drive-side cam 29 and driven-side cam 30 of the cam device 27. The necessary force for holding the displacement bracket 14 with respect to the support bracket 15 differs depending on the diameter of the steering column 6, or in other words, the width dimension of the displacement bracket 14. When the force for holding the displacement bracket 14 with respect to the support bracket 15 differs, the amount of expansion or contraction of the space between the inside surfaces of the pair of support-plate sections 17 differs, so there are different cam devices 27 having various different amounts of expansion or contraction. Adjustment of the amount of expansion or contraction of the cam device 27 is performed by appropriately selecting the height in the axial direction of the drive-side convex sections 36 and driven-side convex sections 38 of the drive side cam 29 and driven-side cam 30. When it is desired to adjust the operational feeling of the adjustment lever 25, an appropriate angle between the inclination angle formed on the rear surface with respect to the unlocking direction of both side surfaces in the circumferential direction of the drive side convex sections 36, and the inclination angle that is formed on the front-side surface with respect to the unlocking direction of both side surfaces in the circumferential direction of the driven-side convex sections 38 is selected.
As described above, there are various kinds of drive-side cams 29 and driven side cams 30, for which the specifications of drive-side cam surface 33 and the driven-side cam surface 34, or in other words, the width in the circumferential direction and height in the axial direction of the driven-side convex sections 36 and the driven-side convex sections 38, and the inclination angle of the inclined surface differ.
In the factory for assembling the steering device, a worker selects and assembles an appropriate combination of a drive-side cam and a driven-side cam one at a time that correspond with each other according to the vehicle type from a case in which plural kinds of drive-side cams and driven-side cams are stored according to each kind. When doing this there is a possibility that one of the cams of the drive-side and driven-side cam will be mistakenly selected (taken mistakenly). In the case that the specifications for the cam surface between the proper cam (cam that was supposed to be selected) and the mistakenly selected cam differ only a little, it will be difficult to determine that there is a mistake (that there is a wrong combination) in the state before the cam device is assembled in the steering device. When it is determined after the steering device has been assembled that a cam was taken by mistake, it becomes necessary to perform the assembly work again from the beginning or part way, and productivity is impaired.
JP2000053001 (A) discloses construction in which by providing stopper protrusions at four locations that are evenly spaced in the circumferential direction of the outer-circumferential edge section of the cam surfaces of the cam members (drive-side cam and driven-side cam) that face each other, and regulating (limiting) the amount of relative rotation between a locking bolt and nut, it is possible to regulate the locked rotation position and unlocked rotation position. However, even in the case of the construction of the invention disclosed in JP2000053001, when one of the cams is taken by mistake, it becomes difficult to determine that the combination is wrong in the state before assembly.